Lesson 6 - Beer Flavour and Stability
In this lesson we will discuss beer flavour and beer flavour stability. This will include the effects raw material has on beer flavour, followed by a discussion on common taints, their flavours and consumer reaction. We will examine the flavour changes that occur during beer storage: focussing on oxidation reactions, the species of oxygen involved, and how we can utilise antioxidants to protect against aged beer flavour change. Finally, we will summarise the selection of raw materials and process optimisations available to improve beer flavour stability.
Adjuncts
Adjuncts are extract sources other than malted barley. Some adjuncts contribute little flavour, and others are very flavour-active.
The type of adjunct used will influence beer flavour. Adjuncts like maize, rice grits or flakes, and sugars impart no flavour and will dilute any coming from the malt. This gives a cleaner, more neutral flavoured beer. However, if not properly de-germed, they may have higher levels of lipids which, as we will see later, can be oxidised – leading to rancid flavours in the material and stale flavour during beer storage.
Liquid adjunct syrups do not contain lipids and will dilute flavour without the risk of lipid oxidation. They can be contaminated by Clostridium bacteria which produce butyric acid described as ‘cheesy’ or ‘baby vomit’.
Dark-coloured liquid adjuncts, for example, caramel and malt extracts, contain melanoidins which protect against oxidation. These products will, by themselves, impart roasted and toasted flavour.
Wheat adjuncts are believed by some to give beer a bready flavour, and some feel rye can give spicy flavours.